1. Field of the Invention
The present invention relates to an anti-theft device for protecting the driver controlled valves serving the air brakes of a vehicle from being manipulated. A clamp assembly is locked on to the valve knobs controlling the air brakes and may be removed only by a key or the like.
2. Description of the Prior Art
U.S. Pat. No. 3,362,426 issued to Charles R. Polit et al. on Jan. 9, 1968 discloses an anti-theft lock valve device which requires a permanently installed housing integrated with said lock valve for either a fuel or braking system. The housing consists of U-shaped sections of sheet metal which must be assembled about the lock valve before said valve is installed in the brake system piping.
U.S. Pat. No. 3,682,195 issued to Degan O. Cvetkovich on Aug. 8, 1972 discloses a wheel lock positioned on the dashboard and interposed in the brake fluid line to at least one wheel brake cylinder of the vehicle.
U.S. Pat. No. 3,998,495 issued to John P. Maxwell et al. on Dec. 21, 1976 discloses a locking dashboard control valve for selectively establishing connections between the spring applied parking brake in an air braked vehicle and either the parking brake air reservoir or the exhaust port of the control valve, and incorporating a lock which enables the operator to secure the control valve in the position in which the parking brakes are applied.
U.S. Pat. No. 4,454,934 issued to Joseph E. Deveney et al. on Jun. 19, 1984 discloses a remotely controlled lock on a rotatable valve stem for use in a nuclear processing plant.
U.S. Pat. No. 4,519,653 issued to Paul B. Smith on May 28, 1985 discloses an additional parking brake control knob on the dashboard which operates the ignition system to permit the release of the parking brakes.
U.S. Pat. No. 4,543,984 issued to John M. Murray on Oct. 1, 1985 discloses a permanently installed lock box enclosing the valve for maintaining brake-on air pressure and mounted on the truck trailer.
U.S. Pat. No. 4,621,874 issued to Jan Gustafsson on Nov. 11, 1986 discloses a three-way valve as an anti-theft device for the deceleration brakes and parking brake controlled by a code lock.
U.S. Pat. No. 4,633,686 issued to Wesley G. Carr on Jan. 6, 1987 discloses an anti-theft brake lock which is key operated and integrated with the hydraulic fluid system.
U.S. Pat. No. 5,145,240 issued to Ronald L. Harless et al. discloses an air brake safety and anti-theft valve assembly which is permanently installed on the trailer and includes valve means for selectively venting the air supply line to the atmosphere in order to prevent the release of the air brakes.
Japanese Patent No. 63-103752 issued to Satoshi Arimitsu on May 9, 1988 discloses a brake valve device which maintains brake cylinder pressure by control from a switch.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. The patents fail to disclose a guard device comprising a clamp which is portable and blocks access to the air brake control knobs in the cabin of the tractor-trailer vehicle. Further, the prior art fails to disclose the novel feature of utilizing inserts in the guard device which enable adaptability to other standard valve knob systems.